Brush for dynamo-electric machines.



Uniran STATES PATENT carica.'

i EMERY G. GILSON, E SCHENETADY, NEW YORK, ASSIGNOR T O GENERAL ELECTRIC COMPANY, A CORPORATION 0F NEW YORK.

` y BRUSH ron. Dynamo F.Lize'in'Icy MACHINES. *y f To all whom, itmay @cavern Be it known that; I, EMERY G. GrLsoN, a citizen of the United States, residing at Schenectady, county of Schenectady, State lof New York, have invented certain new Vand useful Improvements in Brushes for Dynamo-Electric Machines, of which "the following is a specification. v

The present invention relatesto bearing .metals, suited particularly for brushes, or other rubbing parts of' dynamo-electric niachines, and is an improvement on' the material described in 'my Patent No. 1,071,044, of August 26, 1913.

scribed, consisting of copper, graphite and a soft alloying metal, while entirely satisfactoryv for brushes used on collector rings of alternating currentmachines, is not so-well suited for commutating machines in which the circuit is continuously shifted' from one vcommutator segment to another. Under such conditions of operation there occurs a roughening of the commutator, which is apparently due t'o a deposition of metal from the brush to the commutator segments,

-and also to inequality of wear of the bars and the mica spacers. This roughening causes sparking which in turn makes the deposition of metal more pronounced,y so that great care is required/,to keep the comlmutator in satisfactorycondition. I have found that when a small amount of a metal less easily vaporized by thespark than copper, such as iron, nickel, chrommm, manganese, tungsten or the like, is added to the brush mixture that uniformly good commutation can be secured.

The `accompanying drawing illustrates a metal brush of a typeto which my invention is applicable.

In carrying out my` invention, I prefer to begin with aniixture of copper oxid, and an excess of graphite to which there is, added usually also some reducible. compound of a soft alloying metal, for example, lead or tin oxid. This mixture is heated to a reducing temperature until all but a small amount of the 'compounds have been reduced to the metallic state. The iron or equivalent metal is then added, preferably as the oxid. The

mixture is :finally p ressed andred as will y explained.

be more full Although I do not Ywish to be limited by Specification of Letters Patent.

The bearing composition therein de any specific proportions or other details, I w1ll describe a brush mixture which may be considered as typical of my invention'. A

copper oxid, CuZO, 95 parts of graphite, 127 parts of tin oxid and 81 -parts of lea-d oxid or other soft metal which will readily alloy vwith the copper. If some other oxids are used the graphite content should be varied in accordance withvthe oxygen content of the oxid, so as to leave substantially the brush@ These materials should be in a finely divided condition and ,may thoroughly mixed'by pulverizing them in a ball mill or similar device. The mixture is placed, in a .suitable retort, for exampleV a copper retort and is heated labout 5 to 8 hours to a temperature of about 650 C. At the end of this time a large part of the met-allie compounds will have been .reduced to the metallic state but the reduction should be stopped before complete reduction has taken place. The amount of unreduced oxid may vary somewhat with the character of the mixture and the other details of the process but usually.` the mixture should ntain somewhere between 1.5 to 3.5% of nreduced oxid, or other compound. In some cases the oxid percentage may be somewhat higher. The length of time necessary to effect the desired reduction will vary in accordance with the character of the mixture. Uponl cooling preferably about one. to .four parts of iron oxid Fe203, in a niy powdered 'state are added for every 100 parts of the above de` scribed reduced mixture, but the iron oxid admixture may be high enough to leave 5% of iron in the finished brush. The iron oxid is thorXughly distributed in any convenient manner. The mixture is put through a 100 mesh sieve and is then compressed into desired form. The compressed articles are lired under the exclusion of air to a temperature of`650to'700o C. until the reduction of the oxids is substantially complete and consolidation and alloyagehas taken place between the metal particles comprising the mixture.

articles are' packed in charcoal and heated slowly so that the temperature of 650 to 700 C. is reached in' about 18 hoursthe heating being then continued about 120 lIt is likely that the iron is present hours.

v Patented Apr. 21, 1914. Application filed January 29, 1913. Serial No. 745,921.

mixture is prepared of-1000 parts of'redA same amount of graphite in the finished Preferably the` shaped l has the eii'ect of reducin in the finished brubh in the form of a carbid although it may also alloy itself at leastl to some extent with the copper. In` whatture' of metals, I wish it to beunderstood ,that various substitutions may be made, for

example, silver may be substituted for copper and the alloying metals may be replaced by others or even left out entirely. Compounds of iron other than the specific oxid mentioned may be used,'in fact, as already indicated metals other than 4iron may be used as an addition to the composition to produce the above described result, although I prefer iron, or some other metal of the same group. Whereas the appended claims call specifically for a'YA mixture containing iron, as' an elementary constituent I-mean 1;.A brushfor dynamo-electric machines conslsting' of copper, an alloying metal softer than copper, a lubricating substance,

'and a few per cent. of iron.

2.- A current collector consisting of copper, a soft alloying metal, graphite and about 2 to 5 per cent. of iron.

3. A brush for dynamo electric machines comprising a molded mass of metal particles consolidated by heating and containing copper, a soft alloying metal and a substantial amount of iron as elementary constituents. t

4. A brush for dynamo electric machines, comprising copper, graphite, tin and more than a trace of iron as elementary constituents. l

In witness whereof, I have hereunto set my hand this 27th day of January, 1913.

EMERY G. GILSON.

Witnesses:

BENJAMIN B. HULL, HELEN ORFoRD. 

